Information is increasingly being created, exchanged and stored in the eXtensible Markup Language (XML). XML is suitable for this purpose because of its flexibility and self-describing nature. Namely, it is human readable, while at the same time it is convenient for machine processing. Examples of XML-based information include a large number and variety of electronic newspapers, technical journals, bibliographical databases, and healthcare databases. Almost every Internet web site run by large organizations with useful information content makes this information available as XML now.
These information sources are typically geographically dispersed across a network, as are the potential consumers of this information. Communicating XML-based information presents opportunities and challenges from a networking perspective. A network that can efficiently forward XML data can be advantageous, as it can offload the filtering of tremendous volumes of data from consumers. Or, it can reduce the load on the source and the network, by avoiding sources having to broadcast information to individual consumers. Using network layer IP multicast, while alleviating the problem somewhat, is not efficient enough because it results in traffic concentration, especially in an environment with a large number of sources.
Commercially, DATAPOWER offers network appliances that accelerate XML parsing, validation, and encryption. SARVEGA also offers an appliance for XML subscription processing. SEMANDEX offers appliances that can be connected into a network, and used for routing a query to relevant data sources. However, certain of these require that queries use a proprietary XML dialect for describing and querying content, and, in various of these solutions, the queries are processed by each router en-route.
Accordingly, there is a need for a system for content access and distribution that addresses certain shortcomings of existing technologies.